I'm 5'4" and ride a 54TT/54ST. While I'm riding, it fits just fine and I notice no discomfort. But if I try to stand with both feet on the ground, I have to lift my heels by like a centimeter for the top tube not to touch.

Basically, if it's comfy when you ride it (after adjusting everything), then don't worry about it.

And really, the only issue with a "large" frame is that your saddle-bar drop is limited, but I prefer a small drop.